1. Field of Invention
This invention relates to ellipsometry. More particularly, it relates to a novel ellipsometer and ellipsometry analysis technique that allow the dielectric constant and the complex index of refraction for a sample material to be determined without the need for wavelength dependent numerical approximations and frequency scans.
2. Background
Ellipsometry techniques are based upon the fact that a linearly-polarized light vibration may be resolved into two perpendicular vibrations that are in phase. One of these vibrations is in the incidence plane and the other is in a plane normal to the incidence plane. After reflection or transmission, these vibrations undergo amplitude and phase changes which are generally different. Thus, the light is then elliptically-polarized. An ellipsometer generally measures the changes in the state of polarization and includes a monochromatic light source, collimators, a polarizer with or without a quarter wavelength plate, a surface, an analyzer and a photo detector.
The polarization of the light reflecting off a sample is measured and analyzed to determine the variations in that polarization from the incident light. For this analysis, existing techniques generally have used a polarizer, a quarter wavelength plate, and an analyzer. The polarizer and the analyzer are rotated to obtain the respective angles for the polarizer and the analyzer at which the reflected light from the sample is extinguished by the analyzer. From these angles, the variables of polarized light can be calculated, such as the phase difference (delta) and the amplitude-reflection ratio angle (psi).
Prior ellipsometry techniques are often used to determine the thickness of thin films on solid materials, such as an oxide layer thickness on a semiconductor material. Prior ellipsometry techniques, devices and analyses, however, require the use of numerical approximations to determine certain properties of the sample material, such as the dielectric constant and complex index of refraction. Further, prior ellipsometry techniques, devices and analyses do not provide for the quick, direct, and accurate analysis of spectroscopic properties of sample materials, including properties of biological fluids, such as the saline content in a blood sample.
The object of the present invention is to provide a novel ellipsometer device and ellipsometry technique that allows the direct determination of optical and spectroscopic properties of sample materials, such as the complex dielectric constant and complex index of refraction.